# Symmetry and conservation laws related to baryon number, lepton number and strangeness

According to Noether's theorem, Every continuous symmetry of the action leads to a conservation law. For example, conservation of linear momentum corresponds to translational symmetry, conservation of angular momentum corresponds to rotational symmetry.

My question is on the conservation of baryon number, lepton number and strangeness. What type of symmetry does imply when the above mentioned quantities are conserved in a system?

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–  Qmechanic Oct 1 '12 at 6:16
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## 1 Answer

Conservation of baryon number <-> Global gauge invariance

Conservation of lepton number <-> U(1) symmetry

Conservation of strangeness is only for the strong (SU(3) symmetry) and electromagnetic interactions ( local U(1) gauge invariance)

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Please don't call it "global gauge invariance", it's a phase rotation of the baryon wavefunctions, which is not really a "gauge transformation", it's a global field transformation. You are not describing the symmetry, you are only giving it a suboptimal name. –  Ron Maimon Oct 1 '12 at 7:07
@MANIKANTABORAH: I am not a "sir", I am a "dude", and this answer is complete and correct, it is just using annoying terminology. If you want a different answer, one could explain a little more, but it's easier if you just learn how to write down the standard model in 2 component notation, it will then be obvious--- it's also covered in the answers to the linked questions. –  Ron Maimon Oct 4 '12 at 18:03
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